Merge pull request rails#49187 from ccutrer/defer-constraints

Add `set_constraints` helper for PostgreSQL

Author: yahonda

activerecord/CHANGELOG.md

@@ -1,3 +1,19 @@
+*   Add `set_constraints` helper for PostgreSQL
+
+    ```ruby
+    Post.create!(user_id: -1) # => ActiveRecord::InvalidForeignKey
+
+    Post.transaction do
+      Post.connection.set_constraints(:deferred)
+      p = Post.create!(user_id: -1)
+      u = User.create!
+      p.user = u
+      p.save!
+    end
+    ```
+
+    *Cody Cutrer*
+
 *   Include `ActiveModel::API` in `ActiveRecord::Base`
 
     *Sean Doyle*

activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb

@@ -132,6 +132,27 @@ def build_explain_clause(options = [])
           "EXPLAIN (#{options.join(", ").upcase})"
         end
 
+        # Set when constraints will be checked for the current transaction.
+        #
+        # Not passing any specific constraint names will set the value for all deferrable constraints.
+        #
+        # [<tt>deferred</tt>]
+        #   Valid values are +:deferred+ or +:immediate+.
+        #
+        # See https://www.postgresql.org/docs/current/sql-set-constraints.html
+        def set_constraints(deferred, *constraints)
+          unless %i[deferred immediate].include?(deferred)
+            raise ArgumentError, "deferred must be :deferred or :immediate"
+          end
+
+          constraints = if constraints.empty?
+            "ALL"
+          else
+            constraints.map { |c| quote_table_name(c) }.join(", ")
+          end
+          execute("SET CONSTRAINTS #{constraints} #{deferred.to_s.upcase}")
+        end
+
         private
           IDLE_TRANSACTION_STATUSES = [PG::PQTRANS_IDLE, PG::PQTRANS_INTRANS, PG::PQTRANS_INERROR]
           private_constant :IDLE_TRANSACTION_STATUSES

activerecord/test/cases/adapters/postgresql/deferred_constraints_test.rb

@@ -0,0 +1,55 @@
+# frozen_string_literal: true
+
+require "cases/helper"
+require "models/author"
+
+class PostgresqlDeferredConstraintsTest < ActiveRecord::PostgreSQLTestCase
+  def setup
+    @connection = ActiveRecord::Base.connection
+    @fk = @connection.foreign_keys("authors").first.name
+    @other_fk = @connection.foreign_keys("lessons_students").first.name
+  end
+
+  def test_defer_constraints
+    assert_raises ActiveRecord::InvalidForeignKey do
+      @connection.set_constraints(:deferred)
+      assert_nothing_raised do
+        Author.create!(author_address_id: -1, name: "John Doe")
+      end
+      @connection.set_constraints(:immediate)
+    end
+  end
+
+  def test_defer_constraints_with_specific_fk
+    assert_raises ActiveRecord::InvalidForeignKey do
+      @connection.set_constraints(:deferred, @fk)
+      assert_nothing_raised do
+        Author.create!(author_address_id: -1, name: "John Doe")
+      end
+      @connection.set_constraints(:immediate, @fk)
+    end
+  end
+
+  def test_defer_constraints_with_multiple_fks
+    assert_raises ActiveRecord::InvalidForeignKey do
+      @connection.set_constraints(:deferred, @other_fk, @fk)
+      assert_nothing_raised do
+        Author.create!(author_address_id: -1, name: "John Doe")
+      end
+      @connection.set_constraints(:immediate, @other_fk, @fk)
+    end
+  end
+
+  def test_defer_constraints_only_defers_single_fk
+    @connection.set_constraints(:deferred, @other_fk)
+    assert_raises ActiveRecord::InvalidForeignKey do
+      Author.create!(author_address_id: -1, name: "John Doe")
+    end
+  end
+
+  def test_set_constraints_requires_valid_value
+    assert_raises ArgumentError do
+      @connection.set_constraints(:invalid)
+    end
+  end
+end

activerecord/test/cases/migration/exclusion_constraint_test.rb

@@ -162,7 +162,7 @@ def test_added_deferrable_initially_immediate_exclusion_constraint
 
           assert_nothing_raised do
             Invoice.transaction(requires_new: true) do
-              Invoice.connection.exec_query("SET CONSTRAINTS invoices_date_overlap DEFERRED")
+              Invoice.connection.set_constraints(:deferred, "invoices_date_overlap")
               Invoice.create!(start_date: "2020-12-31", end_date: "2021-01-01")
               invoice.update!(end_date: "2020-12-31")
 

activerecord/test/schema/schema.rb

@@ -97,7 +97,7 @@
   create_table :author_addresses, force: true do |t|
   end
 
-  add_foreign_key :authors, :author_addresses
+  add_foreign_key :authors, :author_addresses, deferrable: :immediate
 
   create_table :author_favorites, force: true do |t|
     t.column :author_id, :integer
@@ -706,7 +706,7 @@
     t.integer :college_id
   end
 
-  add_foreign_key :lessons_students, :students, on_delete: :cascade
+  add_foreign_key :lessons_students, :students, on_delete: :cascade, deferrable: :immediate
 
   create_table :lint_models, force: true
 

guides/source/active_record_postgresql.md

@@ -633,11 +633,11 @@ ActiveRecord::Base.connection.transaction do
 end
 ```
 
-When the `:deferrable` option is set to `:immediate`, let the foreign keys keep the default behavior of checking the constraint immediately, but allow manually deferring the checks using `SET CONSTRAINTS ALL DEFERRED` within a transaction. This will cause the foreign keys to be checked when the transaction is committed:
+When the `:deferrable` option is set to `:immediate`, let the foreign keys keep the default behavior of checking the constraint immediately, but allow manually deferring the checks using `set_constraints` within a transaction. This will cause the foreign keys to be checked when the transaction is committed:
 
 ```ruby
-ActiveRecord::Base.transaction do
-  ActiveRecord::Base.connection.execute("SET CONSTRAINTS ALL DEFERRED")
+ActiveRecord::Base.connection.transaction do
+  ActiveRecord::Base.connection.set_constraints(:deferred)
   person = Person.create(alias_id: SecureRandom.uuid, name: "John Doe")
   Alias.create(id: person.alias_id, person_id: person.id, name: "jaydee")
 end